The benefits of swimming are numerous: Swimming is the perfect, low-impact form of exercise. Nearly anyone can practice simple swimming moves in a pool and burn calories without injuring backs, knees or shoulders. And if you’ve ever spent a day in the pool, in the lake or in the surf, you know how conducive this activity is to sleep. But why is that? Why do we sleep better after a day spent in the water? There’s actually a science behind it:

Cold Water Lowers Body Temperature

The fresh, cool water of the local pool feels so good on a hot day because it lowers your body temperature. When your body temperature drops, your body must fight harder to try to raise it, meaning it burns more calories and uses more energy. This, in turn, brings on that cozy, fatigued feeling most people get after swimming.

Sun Exposure Raises Body Temperature

Just as all day spent in and out of a cool body of water lowers your body temperature, a day spent on and off the sand can raise it. Both will make your body work harder to regulate its temperature which means more fatigue for you. So if you’re combining hours spent lounging on the beach under a hot sun with hours spent frolicking in the cool surf, expect to be extra-sleepy when you finally head indoors.

Exercise Relaxes Your Psyche

More exercise is often a recommendation for people who suffer from insomnia. Why? Because exercise has been directly linked to lowered levels of depression and anxiety. Regular, daily exercise can also help shift a person’s circadian rhythm, making it easier for people who typically stay up all night and sleep through the day to reverse the process.

Swimming is Stellar Exercise

If you’re looking at swimming as a solution for how to get sleepy, opt for endurance techniques like swimming from end to end of the pool, treading water in place or practicing a simple backstroke. Diving is another option for anyone who’s in good physical condition. Any exercise that gets you up and down the steps and in and out of the pool repeatedly is aces for wearing you out and helping you sleep.

Swimming Gets You Outside and Around People

Depression can be a major contributor to insomnia, and yet it’s a vicious cycle — the lower you feel, the less you want to go out, do things and be around people. But in fact, this strategy might be just what you need. Swimming not only gets you poolside or beach-side, it also exposes you to the sun’s rays that are packed full of vitamin D. Vitamin D is something your body needs to help stave off chronic illnesses such as heart disease and cancer. And it’s sun-deficit that helps lead to Seasonal Affective Disorder, or SAD, that can interrupt your sleep cycle and circadian rhythm. Getting enough sunlight — at least 15 minutes daily — is crucial for good health and a happy disposition.

The next time you find your morning ruined by an inability to get a restful night’s sleep, toss your beach towel in a bag and slip into your swimsuit. Head out for a relaxing day at the pool or the beach or the lake. If all goes according to plan, you’ll sleep like a baby when you return home.